The present invention relates generally to a method for repairing a pipeline, such as a sewer pipe, by installing a liner inside of the pipeline. More specifically, the present invention relates to a process wherein a curable resin system is applied to the inside walls of the pipeline in a two part process where a first resin is spun onto the pipeline wall and a second resin is coated onto a flexible fabric liner that is then installed into the pipeline.
Throughout developed parts of the world, there are numerous pipeline conduits that run underground in order to provide utility services to businesses and residences. These utilities include water lines, sewer pipes, storm water drains, and the like. Since these pipelines are installed underground, they are constantly subjected to numerous environmental pressured that cause the pipeline to deteriorate. For example, the pipeline may deteriorate due to ordinary aging, corrosive action of the fluids being transported in the line, environmental conditions such as groundwater exposure, or other reasons. Over time, all of the wear factors that impact on the pipeline result in holes, cracks, and other defects in the line that must be repaired in order to prevent fluid leakage problems.
In some instances, the concern is that foreign matter, which is initially part of the actual construction of the pipeline, may begin to flake off of the interior surfaces of the damaged pipeline and enter the fluid flow within the pipeline. For example, ductile iron piping has a clay liner surface that upon failure may allow rust to enter the fluid flow. Similarly, transite pipes that contain asbestos reinforcing fibers may release asbestos into the drinking water contained therein as the wall of the pipe begins to deteriorate. Finally, the potential exists for the introduction of substances that flow from the surrounding underground environment into the pipeline or for the water that is being carried through the pipeline conduit to flow outwardly through the cracks leading to a loss of water pressure and other problems.
The traditional approach to repairing the above-identified issues entailed digging up the effected pipeline and replacing it. Given the millions of miles of installed pipeline in the United States alone, this solution would be prohibitively expensive. Further, such pipelines are typically located beneath streets and right of ways where digging would create traffic flow problems and require extensive repaving of roadways as the replacement process was completed. In the case where transite pipelines must be repaired, an additional issue regarding the need to dispose of large quantities of asbestos waste must be addressed.
In an attempt to overcome many of these problems related to the traditional digging methods, a number of methods for renovating existing underground pipelines have been developed. Many of these methods employ the installation of a lining on the interior of the damaged pipeline using a lining hose and a calibration hose. For example, U.S. Pat. No. 4,714,095 (Müller) discloses a method of salvaging an underground sewer pipe with a lining hose and calibrating hose. The lining hose includes an inner layer, which is treated with a first resin, and an outer layer, which is not treated with a resin. The lining hose is placed into the pipe conduit. A surface region of a calibrating hose, which will contact the inner layer of the lining hose, is coated with a second resin. Then, the calibrating hose is introduced into the lining hose. The resins harden so that the lining hose becomes attached to contact surfaces of the calibration hose.
U.S. Pat. No. 4,770,562 (Müller) discloses another method of salvaging an underground pipe conduit. A lining hose having an inner layer that is saturated with a resin is used. The lining hose includes an outer layer, which is perforated to form flow-through openings for the resin of the inner layer. The lining hose is introduced into the pipe conduit. Then, the lining hose is shaped to conform to the pipe by introducing an auxiliary hose into the lining hose and injecting fluid into the auxiliary hose. The resins harden to form a lining structure in the pipeline. After the curing step, the auxiliary hose can be kept in the lining hose or it can be removed using ropes or cables.
U.S. Pat. No. 5,653,555 (Catallo) discloses a method of lining a pipe conduit using multiple curing resins. A lining hose, which is coated with a high-strength resin, is first positioned inside of the conduit. The lining hose is then expanded into contact with the inside surface of the conduit by inverting a calibration hose. The calibration hose has a layer of corrosion-resistant resin. The high-strength and corrosion-resistant resin layers are cured by the application of a heated fluid. The cured lining hose and calibration hose form a rigid self-supporting structure. The calibration hose is not removed from the liner.
U.S. Pat. No. 5,680,885 (Catallo) discloses a method of rehabilitating a damaged pipe conduit using a lining hose and calibration hose. The inner layer of the lining hose is soaked with an excess volume of resin. The calibration hose contains a resin-absorbent layer. The calibration hose is placed in the lining hose and inverted by the application of heated water. After inversion, the resin-absorbent layer of the calibration hose contacts and adheres to the resin-coated layer of the lining hose. Upon curing, the calibration hose becomes an integral part of the liner.
U.S. Pat. No. 5,706,861 (Wood) discloses a method of lining a section of a pipeline by a “cured in place” system using a lining tube and inflatable bladder. The lining tube is impregnated with a curable synthetic resin and carried into the pipe conduit on an annular inflatable bladder. The bladder is inflated and the lining tube is cured to the pipeline. Then, the bladder is peeled away from the cured lining tube and removed from the pipe conduit by ropes.
Although the above-described conventional methods may be somewhat effective in repairing pipelines, they still suffer from various problems. For example, problems arise concerning the inversion of a felt liner because it is relatively delicate and tends to break or rip during the inversion process. Also, pulling prior art liner tubes around corners is very difficult resulting in fractures in the sealing at such joints. Also, the pipeline joints found at corners and periodically along the length of the pipeline forms voids that cannot be completely filled by the prior art methods. Thus, the prior art methods can do nothing to improve the strength of the pipeline at its joints. Another difficulty is that once a liner has been installed, the identification of lateral supply pipe branches are difficult to identify and clear.
In view of the foregoing, there is a desire for a structural lining process that effectively seals all of the leaks and cracks within a pipeline. It is also desirable to provide a lining process that preserves structural integrity of the liners throughout the length of the pipeline, including tight bend and turn locations within the pipeline. It is also desirable to improve the adhesion between the lining hose inside of the pipeline and the interior walls of the pipeline to ensure integrity of the liner for a permanent installation that does not need periodic repair. It is also desirable to provide a lining system that enhances the installer's ability to identify and clear the various piping laterals along the pipeline system.